Mechanisms of Memory Triage during Sleep

乍一看，睡眠似乎是进化的一个不适应步骤。睡眠使动物长时间处于“不活动”状态，减少了动物用于觅食、狩猎和寻找/吸引配偶的时间。此外，睡眠比保持清醒更危险，因为保护我们免受捕食的感觉输入被抑制了。那么，我们能得到什么回报呢？简短的回答是，我们不知道。很明显，进化使睡眠成为一种生物需求。你的大脑不会让你自愿避免睡眠超过几个晚上，非自愿的睡眠剥夺会导致慢性压力，疲劳，迷失方向，健康状况不佳，甚至死亡。然而，尽管经过了几十年的研究，我们仍然没有完全理解为什么我们有这种睡眠的生理需求。睡眠可能扮演着多种角色，这得益于长时间的“离线”状态和减少的感官输入。一个主要的假设功能是系统水平的记忆巩固，通过这个过程，存储在海马体中的新记忆被稳定并转移到新皮层大脑区域进行长期存储。记忆巩固的一个关键方面是记忆分类现象，通过这种现象，与不相关的经验相比，突出或重复的经验更有可能被巩固。大脑是如何选择性地强化重要记忆的，目前还不清楚，这也是我们研究计划的重点。我们观察到，在一次经历中发生的神经活动的顺序模式，在睡眠中会自发地重新激活。这种被重新激活的记忆痕迹，被称为重放，被认为是大脑巩固记忆的方式，将海马体中的记忆转移到其他大脑区域。我们将研究如何通过经验的显著性来调节重放，并假设更重要的经验将在睡眠期间重放更多。此外，我们预测，皮层反馈在调制重放的基础上的显着性起着关键作用。为了验证这一点，我们将对海马体的皮层输入进行重新定位，并检查海马体是否不再偏向于更突出的体验。大约70%的布里茨每晚睡眠时间少于医学界推荐的7-9小时。此外，社交媒体使用的增加与睡眠质量较差有关，沿着焦虑和抑郁的发生率增加。随着我们生活中“垃圾信息”的增加，以及我们睡眠时间的减少，我们的记忆分类系统面临着越来越大的压力，需要有效地优先整合突出信息，并且越来越需要了解这是如何发生的。这些问题在老年人中进一步恶化，因为睡眠质量和持续时间都随着年龄的增长而下降。我们的研究将直接研究记忆分类的潜在机制，并就如何进一步优化这一过程提供新的思路。

At first glance, sleep appears to be a maladaptive step of evolution. Sleep imposes a prolonged period of "inactivity", reducing the time an animal can spend on foraging, hunting, and finding/attracting mates. Furthermore, sleep is substantially more dangerous than staying awake, as the very sensory inputs protecting us from predation are suppressed. So, what then do we get in return? The short answer is that we do not know. It is clear that evolution has made sleep a biological requirement. Your brain will not let you voluntarily avoid sleeping more than a few nights, and involuntary sleep deprivation leads to chronic stress, fatigue, disorientation, poor health and even death. However, in spite of decades of research, we still do not fully understand why we have this biological need to sleep.Sleep likely serves a multitude of roles benefiting from a prolonged "offline" state with reduced sensory inputs. One major hypothesized function is systems-level memory consolidation, a process by which new memories stored in the hippocampus are stabilized and transferred to neocortical brain regions for long-term storage. One key aspect of memory consolidation is the phenomenon of memory triage, by which salient or repeated experiences are more likely to be consolidated compared to irrelevant experiences. How the brain accomplishes this selective strengthening of important memories is unknown, and the focus of our research proposal.Sequential patterns of neural activity occurring during an experience have been observed to spontaneously reactivate during sleep. This reactivated memory trace, referred to as replay, is postulated to be how the brain consolidates a memory, with the transfer of a memory residing in the hippocampus to other brain regions. We will examine how replay is modulated by an experience's salience, and hypothesize that more important experiences will replay more during sleep. Furthermore, we predict that cortical feedback plays a key role in modulating replay based on salience. To test this, we will inactivate cortical inputs to the hippocampus and examine whether the hippocampus no longer biases replay towards more salient experiences.Approximately 70% of Brits sleep less than the 7-9 hours per night recommend by the medical community. Furthermore, increased social media use is correlated with poorer sleep quality, along with an increased occurrence of anxiety and depression. As the amount of "junk information" in our lives increases, and the amount we sleep decreases, there is a growing pressure on our memory triage system to effectively prioritize the consolidation of salient information, and an increased need to understand how this occurs. These issues are exasperated further in older individuals, as both sleep quality and duration decline with age. Our research will directly examine the underlying mechanisms of memory triage, and provide new ideas on how this process could be further optimised.